1. Technical Field
The present invention relates to a process for manufacturing an interaction structure for a storage medium, in particular for “probe storage” applications, to which the ensuing treatment will make explicit reference without, however, this implying any loss of generality.
2. Description of the Related Art
As is known, storage systems using a magnetism-based technology, such as, for example, hard disks, suffer from major limitations as regards the increase in data-storage capacity, the read/write speed, and size reduction. In particular, a physical limit exists, referred to as “superparamagnetic limit”, which hinders reduction in the dimensions of the magnetic-storage domains below a critical threshold without running the risk of losing the stored information.
In the last few years alternative storage systems have consequently been proposed, amongst which the so-called “probe storage” systems (referred to also as “atomic storage” systems) have assumed particular importance. These systems enable high data-storage capacities to be achieved with small overall dimensions and with low manufacturing costs.
In brief (see FIG. 1), a “probe storage” device comprises a two-dimensional array of transducers (or probes) 2 fixed to a common substrate 3, made, for example, of silicon, arranged above a storage medium 4 and movable with respect to the storage medium, generally in two orthogonal directions, due to the action of a micromotor associated therewith. Each transducer 2 is provided with a supporting element 5 made of semiconductor material, in particular silicon, generally known as “cantilever”, which is suspended in cantilever fashion above the storage medium 4 and carries at one free end an interaction structure 6 (referred to also as “sensor structure” or “contact structure”) facing the storage medium 4. In particular, by the term “interaction” is meant herein any operation of reading, writing or erasure that implies an exchange of signals between the interaction structure and the storage medium. Via the respective interaction structure 6, each transducer 2 is able to interact locally with a portion of the storage medium, for reading/writing/erasing individual bits of information.
The physical characteristics (hardness, roughness, etc.), morphological characteristics (dimensions, shape, etc.), and electrical characteristics (resistivity, thermal conductivity, etc.) of the interaction structure 6 are strictly correlated to the material of the storage medium with which they are associated (polymeric material, ferroelectric material, phase-change material, etc.), and to the mechanisms of interaction for reading/writing/erasing of data (thermal process, passage of charge, etc.).
For example, in some storage systems of the “probe storage” type reading/writing of the individual bits is carried out by interacting with the storage material via a passage of electrical charges through the interaction structure. In particular, in the case where ferroelectric storage media are used, the read operations are destructive, i.e., they imply removal of the stored information and the impossibility for carrying out any subsequent reading of the same data. In fact, reading of a portion of the memory (or trace) corresponds to writing in said portion of memory a sequence of charges that are all positive (or all negative, according to the polarization of an interaction structure). Consequently, during reading, the flow of the read data is stored in a memory buffer, the dimensions of which are at least the same as the dimensions of the trace that is being read. In addition, the contents of the memory buffer are subsequently re-written on the previously read trace, so that the interaction structure is re-positioned at the beginning of the trace, re-writes the entire trace, and subsequently can start a new read operation.